System and method for digital data communication

ABSTRACT

A plurality of HTML files having their file names which may directly be recognized by a filtering part  415  in a data receiver are stored in a data storage part  411.  File names of the HTML files are assigned to their headers by a data converter  412,  and the files converted and multiplexed are repeatedly transmitted by a data multiplexing and transmitting part  413.  A filtering part  415  selects the data having exact match with the filtering condition. A data processing part  419  performs data processing required for generating images, and the images thus generated are displayed on a screen of the display part  421.  The data processing part  419  provides a switching command to a filtering conditions varying part  417  when an operator enters a file to be linked through an input part  420.  The file to be linked is received as a result of changing the filtering conditions. In this way, the files required can be received and be displayed dynamically without storing all the HTML files linked one another even in temporary basis.

This application is a division of application Ser. No. 09/477,735, filedJan. 5, 2000, now U.S. Pat. No. 6,427,150, which is a continuation ofInternational application Serial No. PCT/JP99/02365 filed May 6, 1999,and published as WO 99/57654 on Nov. 11, 1999.

CROSS-REFERENCE TO RELATED APPLICATION

The entire disclosure of Japanese Patent Application No. Hei 10-123193filed on May 6, 1998, another Japanese Patent Application No. Hei10-370637 filed on Dec. 25, 1998, and another Japanese PatentApplication No. Hei 11-107209 filed on Apr. 14, 1999, includingspecification, claims, drawings and abstract is incorporated herein byreference in its entirety.

BACKGROUND OF INVENTION

1. Field of the Invention

This invention relates to digital data communication systems, morespecifically to communications of self-descriptive data.

2. Description of the Related Art

Nowadays, a communication method using the internet is known as two-waydata communications among computers. The principle of the method will bebriefly described hereunder. A plurality of hyper text markup language(hereinafter referred to as HTML) files linked with one another arestored into a world wide web (hereinafter referred to as WWW) serverwhich is connected to the internet. A demand for transmitting the HTMLfiles stored in the WWW server is sent thereto from a gatheringinformation computer which is connected to the internet. The WWW servertransmits whole or a part of the HTML files to the gathering computer inresponse to the demand. As a result, data linked with one another andstored in the WWW server can be transferred.

Data communication services using satellite broadcasting, on the otherhand, are known as one-way data communications. In satellitebroadcasting, data are transmitted through a moving picture expertsgroup 2 (hereinafter referred to as MPEG 2) system standard used fordata transmission which has a relatively higher flexibility than theother two standards in the MPEG 2, such as MPEG 2 video standard usedfor video data and MPEG 2 audio standard used for audio data, out ofthese three MPEG 2 standards.

In order to transmit HTML files to the receivers by using satellitebroadcasting, a demand for transmitting desired HTML file(s) need to besent to the transmitter.

To avoid sending the demand, methods described hereunder are employed inactual data communications protocols such as BITCAST and ADAMS (TV-Asahidata and multimedia service). A plurality of files linked with oneanother are transmitted as one unitized file by the transmitter. In thereceiver, all the files are stored in a storage device like a hard diskby sequentially storing each of the files therein. Further, thespecified file(s) is displayed in response to operation of the user bybrowser software installed in the receiver. The browser softwareperforms reference operations by specifying the name of a file(s) storedin a hard disk when there is HTML tag(s) requiring reference of otherfile(s) in the specified file(s) (details of the technology is disclosedin an article entitled “Special Report from state-of-the-art technology;The Whole Aspect of the Next Generation Digital Television”, publishedby Nikkei Business Publications, Inc.)

In this method, however, all the files must be stored in the hard diskas well as storing information needed to manage the directory. In thisway, a certain capability for storing this information is required inthe receiver, and the receiver can not display a desired file(s) untilits retrieval is completed. Further, a number of processing steps needto be performed by the receiving computer's central processing unit(CPU) for retrieving the desired file(s) from the stored files.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the above mentioneddrawbacks on the data communication method, and to provide a datacommunication system and a method thereof capable of selectivelyreceiving selected data out of data consisting of a plurality of filesrelated one another at a high speed with less data storing capacities.

It is another object of the present invention to provide a datacommunication system and a method thereof capable of selectivelyextracting desired data out of data related with one another even whenthe receiver has a small data storing capability.

In accordance with characteristics of the present invention, there isprovided a digital data communication system comprising a transmitterand a receiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) display data generating means for generating display data accordingto the outputted data, and

b3) selecting condition varying means for varying the selectingcondition; and

C) wherein c1) the file storing means stores files formed ofself-descriptive data which includes a reference command for referringanother file, and wherein the identifier of each file includescharacters directly selected by the selecting condition varying means,

c2) the display data generating means generates display data accordingto the self-descriptive data outputted by the selective receiving means,and

c3) the selecting condition varying means provides an identifierassigned to a file so as to obtain the file specified by the referencecommand in the self-descriptive data to the selective receiving means.

Also, in accordance with characteristics of the present invention, thereis provided a method of communicating digital data, comprising the stepsof:

repeatedly transmitting a plurality of files after packetizing the filesaccording to a transmission protocol with identifiers uniquely assignedthereto in a transmitting station, each of the files comprisingself-descriptive data which include a reference command for referringanother file, the identifier of the each file consisting of charactersdirectly selected by a receiving station, and

performing the following steps in a receiving station, selectivelyreceiving the packetized files having predetermined identifiers inaccordance with a selecting condition set therein, generating displaydata in accordance with the self-descriptive data contained in thepacketized files, outputting the generated data, and varying anidentifier of a file as the selecting condition so as to obtain the filespecified by the reference command in the self-descriptive data.

Further, in accordance with characteristics of the present invention,there is provided a digital data communication system comprising atransmitter and a receiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) received data storing means for storing data contained in thepacketized files each having same identifier in one independent filebasis,

b3) display data generating means for generating display data accordingto the outputted data, and

b4) selecting condition varying means for varying the selectingcondition; and

C) wherein: c1) the file storing means stores files formed ofself-descriptive data which includes a reference command for referringanother file,

c2) the transmission means assigns one module identifier includingcharacters capable of being read directly with the selective receivingmeans to both a reference file which refers other files and a referredfile which is referred by the reference file, and transmits thereference file and the referred file, and

c3) the display data generating means generates display data accordingto the self-descriptive data contained in the reference file, andgenerates another display data according to a desired referred filewhich is read out thereby from the received data storing means.

In accordance with characteristics of the present invention, there isprovided a method of communicating digital data, comprising the stepsof:

repeatedly transmitting a plurality of files stored in a transmittingstation after packetizing the files according to a transmission protocolwith identifiers uniquely assigned thereto in the transmitting station,and

performing the following steps in a receiving station, selectivelyreceiving the packetized files having predetermined module identifiersin accordance with a selecting condition set therein, storing datacontained in the packetized files each having same identifier in oneindependent file basis, and generating display data according to theoutputted data,

wherein one module identifier including characters capable of being readdirectly with the receiving station is assigned to both a reference filewhich refers other files and a referred file which is referred by thereference file in the transmitting station,

wherein the following steps are performed by the receiving station, theselecting condition is varied so as to selectively receive packetizedfiles each assigned same identifier with that of a specific referencefile in order to selectively receive the specific reference file,display data is generated according to self-descriptive data containedin the reference file, and generating another display data according toa desired referred file which is read out thereby.

Also, in accordance with characteristics of the present invention, thereis provided a digital data communication system comprising a transmitterand a receiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) received data storing means for storing data contained in thepacketized files each having same identifier in one independent filebasis,

b3) display data generating means for generating display data accordingto the outputted data, and

b4) selecting condition varying means for varying the selectingcondition; and

C) wherein c1) the file storing means stores a plurality of referencefiles formed of self-descriptive data which includes a reference commandfor referring a plurality of other files,

c2) the transmission means assigns one module identifier includingcharacters capable of being read directly with the selective receivingmeans to the reference files and transmits the reference files,

c3) the display data generating means generates display data accordingto self-descriptive data contained in the reference files, and generatesanother display data according to desired referred files which are readout thereby from the received data storing means, and

c4) the selecting condition varying means uses the module identifier asthe selecting condition.

Further, in accordance with characteristics of the present invention,there is provided a digital data receiver comprising:

selective receiving means for selectively receiving packetized fileshaving predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

received data storing means for storing data contained in the packetizedfiles each having same identifier in one independent file basis;

display data generating means for generating display data according tothe outputted data; and

selecting condition varying means for varying the selecting condition;

wherein the packetized files thus received are one of a reference fileformed of self-descriptive data which includes a reference command forreferring another file and a referred file by the reference file, andone identifier including characters capable of being read directly withthe selective receiving means is assigned to these files,

and wherein the display data generating means generates display dataaccording to self-descriptive data contained in the reference file, andgenerates another display data according to a desired referred filewhich is read out thereby from the received data storing means,

and wherein the selecting condition varying means extracts charactersdirectly be selected by the selective receiving means out of absolutepath assigned to the referred files and provides the characters to theselective receiving means as the selecting condition so as toselectively receive packetized files each assigned same identifier withthat of the reference file in order to selectively receive the referencefile. While the novel features of the invention are set forth in ageneral fashion, both as to organization and content, the invention willbe better understood and appreciated, along with other objects andfeatures thereof from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an overall structure of adata communication system in accordance with the present invention.

FIG. 2 is a simplified conceptual view showing a state of sending radiowaves in satellite broadcasting.

FIG. 3 is a schematic illustration of a transmitter.

FIG. 4 is a view showing a data arrangement of a transport streamtransmitted in satellite broadcasting.

FIG. 5 shows a data structure of packetized data.

FIG. 6 shows contents of control data of control data program map table(PMT) 111 for multiplexing the packetized data.

FIG. 7 shows contents of control data PMT 114 for multiplexing thepacketized data.

FIG. 8 shows contents of control data PAT.

FIG. 9 shows contents of control data network information table(hereinafter referred to as NIT).

FIG. 10 is a schematic block diagram of a receiver.

FIG. 11 is a detailed block diagram illustrating a hardware structure ofthe transmitter.

FIG. 12 shows a file structure stored in an HTML data storage unit.

FIG. 13A, FIG. 13B, and FIG. 13C show contents of HTML files.

FIG. 14A, FIG. 14B, and FIG. 14C are examples of images displayed on ascreen according to the data stored in the HTML files.

FIG. 15 is a correspondence table.

FIG. 16 is a block diagram showing a typical example of the hardwarestructure of a data converter 375.

FIG. 17A and FIG. 17B show other correspondence tables.

FIG. 18 is a flow chart for describing steps for creating thecorrespondence table with the data converter 375.

FIG. 19 is a detailed block diagram illustrating the hardware structureof the receiver.

FIG. 20 is a functional block diagram of a transport stream decoder.

FIG. 21 is a flow chart for describing steps of a receiving operationcontrol program.

FIG. 22 is a flow chart for describing steps of a display program.

FIG. 23A, FIG. 23B, and FIG. 23C are tables showing filteringconditions.

FIG. 24 shows files names after conversion.

FIG. 25A, FIG. 25B, and FIG. 25C show converted contents of HTML files.

FIG. 26 is a flow chart for describing steps for changing a file name.

FIG. 27 is a block diagram showing an overall structure of a digitalbroadcasting system used in a third embodiment of the present invention.

FIG. 28A and FIG. 28B are views showing the structure of the data inboth an HTML file and an U—U object.

FIG. 29 shows a data structure of packetized data being transmitted.

FIG. 30 is a detailed view for describing filtering conditions.

FIG. 31 is a schematic block diagram showing the hardware structure of adata receiver 414.

FIG. 32 is an overall view of a communication system using the datareceiver 414.

FIG. 33 shows data contents of a reference file.

FIG. 34 shows an image displayed according to the contents of thereference file.

FIG. 35 shows a hierarchial tree structure of a file stored in atransmitting station.

FIG. 36 is a flow chart for describing steps of a display program.

FIG. 37 shows data contents of an HTML file in which a plurality offiles are incorporated with one another.

FIG. 38 shows data contents of another HTML file in which a plurality offiles are incorporated one another.

FIG. 39 shows data contents of another HTML file in which referred filesare included therein other than automatic reference tag(s).

FIG. 40 shows a typical image displayed in accordance with the referencefile depicted in FIG. 39.

FIG. 41A and FIG. 41B show data contents of an HTML file which isreferred as the referred file in FIG. 39.

FIG. 42A and FIG. 42B show images displayed according to the referredfile shown in FIG. 41A and FIG. 41B.

FIG. 43 shows a hierarchial tree structure of a file stored in thetransmitter side.

FIG. 44 shows data contents of a reference file.

FIG. 45 shows another hierarchial tree structure of a file stored in thetransmitter side.

FIG. 46 is a flow chart for describing steps of storing data into acache memory.

FIG. 47 shows a data structure of packetized data being transmitted.

FIG. 48A through FIG. 48C show data structure of the data stored in thecache memory.

FIG. 49 shows data contents of an HTML file which is referred as thereferred file.

FIG. 50A and FIG. 50B show images displayed according to the referredfile shown in FIG. 49.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of the present invention will be describedherein along with the index shown in below:

1. FUNCTION BLOCK DIAGRAMS 1 - 1. Outline of satellite broadcasting 1 -1 - 1. State of sending radio waves in satellite broadcasting 1 - 1 - 2.Outline of transmitter 1 - 1 - 3. Structure of transport stream 1 - 1 -4. Outline of receiver 1 - 2. First embodiment 1 - 2 - 1. Transmitter1 - 2 - 2. Receiver 1 - 2 - 2 - 1. Hardware structure 1 - 2 - 2 - 2.Receiving operation control program 1 - 2 - 2 - 3. Display program 1 -3. Second embodiment 1 - 3 - 1. Data converting operations intransmitter 1 - 3 - 2. Data receiving operations in receiver 1 - 4.Third embodiment 1 - 4 - 1. Data transmitter 1 - 4 - 2. Data receiver1 - 4 - 3. Hardware structure of data receiver 1 - 5. Fourth embodiment1 - 6. Other embodiments.

1. Function Blocks

The system 1 shown in FIG. 1 comprises a transmitter 3 and a receiver11.

The transmitter 3 includes file storing means 7 and transmission means5. The file storing means 3 stores a plurality of files comprisingself-descriptive data. A part of the files include reference commandsfor referring another files. Identifiers of the files stored in the filestoring means 7 consist of a series of characters which may directly berecognized with selecting means 15 in the receiver 11. The transmissionmeans 5 repeatedly transmits the files with the identifiers according toa protocol after packetizing them.

The receiver 11 comprises receiving means 14, selecting means 15,display data generating means 19, and selecting conditions variationmeans 17. The receiving means 14 receives the packets thus transmitted.The selecting means 15 selects only packets having selective identifiersout of the received packets in accordance with a selecting condition.The display data generating means 19 generates display data inaccordance with self-descriptive data included in the selected packets.Further, the selecting conditions variation means 17 varies theselecting condition so as to obtain selected file(s) specified by thereference(s) included in the self-descriptive data. The selectingconditions variation means 17 also varies the selecting condition in theselecting means 15 so as to obtain selected file(s) specified by thereference command(s) when an operator of the system selects a displayregion specified by the reference command(s) out of all the regiondisplayed on display means 20.

1-1. Outline of Satellite Broadcasting

One example of applying the present invention to satellite broadcastingwill be described herein. The present invention, however, may also beapplied to other broadcasting methods such as terrestrial broadcasting,wire broadcasting such as cable television and the like as long aspacketized data are transmitted.

1-1-1. State of Sending Radio Waves in Satellite Broadcasting

FIG. 2 shows a simplified conceptual view showing a state of sendingradio waves in satellite broadcasting. Radio waves from a ground station1002 are sent to a plurality of ground receivers (not shown) through abroadcasting satellite 1004. The broadcasting satellite 1004 sends out aplural number of transport streams 1010, 1020, 1030. Each transportstream is distinguished from the others by its frequency, plane ofpolarization and other factors (well known in the art).

A plurality of services (analogous to channels in terrestrialbroadcasting) 1011, 1012, 1013, and 1014 being packetized aremultiplexed in the transport stream 1010 under a time-sharing manner.Similarly, services 1021, 1022, 1023 and 1024, and services 1031, 1032,1033 and 1034 are multiplexed respectively in the transport streams 1020and 1030. Various control data representing service information, thepresent time, and the like, together are sent out to each of thetransport streams in addition to the packetized data (including videodata and audio data). While, FIG. 2 shows only three transport streams,many more transport streams may be sent out. Furthermore, while FIG. 2shows a total of four services multiplexed in each transport stream, inactuality many more services may be multiplexed therein.

1-1-2. Outline of Transmitter

FIG. 3 is a schematic illustration of a transmitter for generating andtransmitting the transport streams described above. While FIG. 3 showsonly the transport stream 1010 for simplicity, other transport instreams 1020, 1030 are generated thereby in the same manner.

Video/audio data of the service 1011 are stored in a data storing unit171. These data are compressed by an encoder 181, and are provided to amultiplexer 160. Similarly, video/audio data of the services 1012 and1013 are stored respectively in data storage unit 172 and 173. Videodata for the services are compressed under the MPEG 2 video standard,and audio data are compressed under the MPEG 2 audio standard. The dataso compressed are provided to the multiplexer 160.

In another data storage unit 174, HTML data used for the service 1014 isstored therein. The data are converted into modules having objectheaders by a data converter 184 in accordance with the MPEG 2 systemstandard. Module identification (module_id) are assigned to each of themodules. Details of the assignment will be described later.

A control data generator 180 generates control data for multiplexing thepacketized data, the control data for displaying program information,the control data representing the present time and other such data. Thecontrol data for multiplexing is assigned for properly recognizingvideo/audio data in plural services which are packetized and multiplexedunder a time sharing manner.

The multiplexer 160 outputs a plurality of packets under a time sharingmanner, each consisting of packetized data having a fixed length as aresult of carrying out packetization of the data provided from thecontrol data generator 180, the encoder 181 through the encoder 183, andthat from the data converter 184, as the transport stream 1010.

Further, the multiplexer 160 assigns individual module_ids to sectionheaders of all the packets when the data from the data converter 184 ispacketized. In this embodiment, the last four digits of a packet areassigned a table_id_extension region (field) by using the first fourdigits thereof as a PID because the module identifiers consist ofdirectory_id and file_id for identifying module (a total of eightdigits) as described later.

Thus, the packets comprising each file can definitely be specifiedwithout further consideration in the receiver by distinguishing themusing the PID and the table_id_extension.

A modulator 164 outputs the packets being provided and modulated therebyas a transport stream. The transport stream thus outputted isbroadcasted to the audience.

1-1-3. Structure of Transport Stream

As shown in FIG. 4, services 1011, 1012 and 1013, each including videodata 81V, 82V and 83V, and audio data 81A, 82A and 83A respectively,service 1014, including HTML or imaging data 84 and a correspondencetable 109 are multiplexed in the transport stream 1010 generated by thetransmitter shown in FIG. 3. Details of the correspondence table 109will be described later.

In addition, control data NIT 100, program allocation table (PAT) 101,and program map table (PMT) 111 through PMT 114 for multiplexing thepacketized data are multiplexed therein. The data corresponding to theservices 1011, 1012, 1013 and 1014 thus multiplexed can be separated byusing these control data as described later. Control data EIT 121through EIT 124, each representing program information, and control datarepresenting the present time TDT 105, are also multiplexed therein.Other control data such as scrambling information and others aremultiplexed therein even though these are not illustrated in thefigures.

The control data PMT 111, PMT 112, PMT 113 and PMT 114, and control dataEIT 121, EIT 122, EIT 123 and EIT 124 are the control data for theservices 1011, 1012, 1013 and 1014 respectively.

Packetization of the control data, the video data, the audio data, HTMLdata and the correspondence table is carried out in the sequence of aline 18 a shown in FIG. 4. In other words, packetization of these datais carried out by the following sequence: the control data NIT, PAT,PMTs, EITs, TDT, then the video data 81V, the audio data 81A, the videodata 82V, the audio data 82A, the video data 83V, the audio data 83, andthe HTML data 84 and the correspondence table 109. Upon completing thepacketization in the first round, further rounds of packetization arecarried out repeatedly under the same sequence starting from the controldata NIT (see line 18 b). The packetization process is carried out undera certain rule being predetermined (not shown).

A basic structure of the packetized data is shown in FIG. 5. Both thecontrol data and the video/audio data being packetized have thestructure as shown in FIG. 5. PIDs are assigned to the forefront of eachpacketized data. PIDs are the references which are uniquely assigned toeach of the packetized data to distinguish each packetized data fromother packetized data. The data content field packetized object data(e.g. the control data, video/audio data, HTML data and others).

Contents of the control data PMT 111 for multiplexing the packetizeddata of service 1011 are shown in FIG. 6. PIDs of both the video data81V and the audio data 81A of the service 1011 are stored in the PMT111. Similar PIDs as to these data in the services 1012, 1013 are storedrespectively to in control data PMT 112, PMT 113.

As shown in FIG. 7, a PID and a module_id (described later) of data 84in the service 1014 are stored in the PMT 114.

PIDs of PMT 111, PMT 112, PMT 113 and PMT 114, each corresponding to theservices 1011, 1012, 1013 and 1014, are stored in the control data PATas shown in FIG. 8.

Transmission specifications defined by their frequencies, planes ofpolarization and the like as to all the transport streams 1010 through1040, and a list of the services multiplexed in each of the transportstreams are described in the control data NIT as shown in FIG. 9. Thisallows the receiver to learn what kinds of services are included in eachof the transport streams.

1-1-4. Outline of Receiver

Functions of the receiver 11 shown in FIG. 1 are outlined with referenceto FIG. 10. In the receiver 11, a desired transport stream is selectedby a tuner 222, and data concerned with a desired service contained inthe selected transport stream is separated therefrom with a transportdecoder 226.

Further, a micro processing unit (hereinafter referred to as MPU) 228sets PIDs of video/audio data of the desired service into the transportdecoder 226. In response to the setting, the transport decoder 226outputs the video/audio data of the desired service. The control datathus separated are provided to the MPU 228 when PIDs of the control dataare set into the transport decoder 226.

Operations of the receiver 1 which currently receives the service 1033contained in the transport stream 1030, and receives a command to switchit to another service 1012 included in the transport stream 1010, willbe described herein.

The MPU 228 controls the transport decoder 226 to obtain the controldata NIT (i.e., by setting a PID of the control data NIT into thetransport decoder 226). The description of the control data NIT tellsthat the service 1012 is multiplexed in the transport stream 1010 (seeFIG. 9). In response to the description, the MPU 228 controls the tuner222 to receive the transport stream 1010. PIDs of video and audio datain the desired service 1012 are obtained as a result of separating thecontrol data PAT and PMT 112 by controlling the transport decoder 226with the MPU 228. The MPU 228 controls the transport decoder 226 tooutput the video and the audio data of the desired service 1012 bysetting filtering conditions (the conditions for performing filtering)to select these PIDs into the transport decoder 226.

Switching of the received service is carried out as described above.

The MPU 228, further controls the transport decoder 226 to obtain thecontrol data EIT when a command for displaying a program schedule andprogram information is provided to the MPU 228. In addition, the MPU 228controls peripherals to display the program information and relatedinformation in accordance with the control data EIT thus obtained.

1-2. First Embodiment

1-2-1. Transmitter

FIG. 11 is a detailed block diagram illustrating a hardware structure ofthe transmitter 3 shown in FIG. 3. The transmitter 3 in this embodimentis used for a digital broadcasting system compliant with MPEG 2standard, Digital Storage Media Command and Control (hereinafterreferred to as DSM-CC) specification, and Digital Video Broadcasting(hereinafter referred to as DVB) specification for Services Information(hereinafter referred to as DVB-SI). Definition of MPEG 2 standard isfound in the international standards organization documents ISO/IEC13818-1 and ISO/IEC 13818-2. The document ISO/IEC 13818-6 specifies theDSM-CC specification. Further, the document ETSI ETS 300 468 (which issimilar to document of Association of Radio Industries and BusinessesSTD-B2 version 1.0 in Japan) defines the DVB-SI specification.

The transmitter 3 is a satellite digital transmitter capable oftransmitting HTML data together with video data and audio data under amultiplexed format. FIG. 11 shows the structures within the transmitter3 supporting the services 1011 and 1014. The structures of services 1012and 1013 (not shown) are similar to that of service 1011.

The video data of the service 1011 is stored in a video data storageunit 311V. The video data are compressed with a video encoder 331. Thevideo data thus compressed is provided to a first-in first-out(hereinafter referred to as FIFO) memory 342 as an elementary stream ata varied rate. The FIFO memory 342 outputs the elementary stream ofvideo data to a packeting circuit 344 at a fixed rate.

The packet circuit 344 segments the elementary stream of the video datainto a plurality of packets each having a fixed length (e.g. 188 bytes),and writes the packets into a memory 352 as packetized elementarystreams (hereinafter referred to as PES). PIDs are assigned to each ofthe PESs as they are written into memory 352.

Similarly, audio data of the service 1011 is stored in an audio datastorage unit 311A. The audio data are compressed with an audio encoder332, and is provided to another FIFO memory 346. The compressed audiodata are segmented into packets by packet circuit 348. Each packet has afixed length, and is written into another memory 354 with its own PID asdescribed above for the video data.

A packet multiplex controller 356 reads out PESs of both the video dataand the audio data stored in the memories 352 and 354 in response to itsencoding speed. Also, the controller 356 provides the PIDs assigned tothe PESs of both the video data and the audio data to a PMT generatingcircuit 358. The PMT generating circuit 358 generates the control dataPMT 111 as a result of receiving the PIDs. The assigned PIDs of both thevideo data and the audio data contained in the service are listed in thecontrol data PMT. Both the PESs of the video and the audio data beingread out from memory 352 and 354 and the corresponding control data PMTare stored in a memory 362 in a multiplex format under a time-sharingmanner.

Thus, the video and the audio data of the service 1011 are multiplexedunder a time-sharing manner and stored in the memory 362.

As shown in FIG. 12, the plurality of HTML files include, e.g., such as“forecast.html”,“today.html” through “osaka.html” and the image filesinclude, e.g., “sun.gif” through “rain.gif”, both stored in a directory“¥weather”. A plurality of HTML and image files are stored in a datastorage unit 314D. In this way, images such as those shown in FIGS. 14Athrough 14C, can be displayed in accordance with the HTML files“forecast.html” “today.html” and “osaka.html” depicted respectively inFIG. 13A through FIG. 13C.

A data converter 375 sequentially assigns individual module identifiersto each of the files. The module identifiers are stored as an objectheader for each file. Data converter 375 also creates a correspondencetable between the module_ids thus assigned and name of the files. Inthis embodiment, file_ids consisting of a total of four digits such asid=“0001” (expressed in hexadecimal) are sequentially assigned to thefiles in the directory “weather” as shown in FIG. 15. The sequentialassignment is made from the top (¥forecast.html) through the bottom file(not shown) of the directory “weather” as described later. Similarly,directory identifiers consisting of four digits such as id=“0001” areassigned to the directory “¥weather” which includes each of the files.Together, the directory_id and the file_id make up the module_id. Thisis to definitely specify each of the files with an absolute pathincluding name of the directory, as shown in FIG. 15. For example, afile “¥forecast.html” can definitely be specified as“¥weather¥forecast.html” “0001/0001”. In this way, a correspondencetable shown in FIG. 15 is created by assigning both the directory_id andthe file_id to each module as its module_id.

The data converter 375 consist of a combination of hardware and softwarestructures in this embodiment. FIG. 16 shows a typical example of thehardware structure of the data converter 375. A corresponding chartshown in FIG. 17A is stored in a ROM 375 r. Steps performed in asoftware structure for data conversion used by the CPU 375 c will bedescribed with reference to FIG. 18.

The CPU 375 c initialize the counter i (step S201, in FIG. 18). Then,the file corresponding to the counter i is stored into the correspondingchart (step S203). For example, the top file “¥forecast.html” of thedirectory “¥weather” is stored into a region representing module number1. Thus, the file “¥weather¥forecast.html” is assigned the module_id“0001/0001” as shown in FIG. 17B. In this embodiment, the moduleidentifiers consist of the four digit file_id=“0001” and the four digitdirectory_id=“0001” as described above.

Next, the CPU 375 c determines whether or not all the files are storedin the corresponding chart (step S207). If files have not been sostored, the CPU 375 c increments the counter i by one, and stores thenext file in the corresponding chart (step S209). Creation of thecorresponding chart is completed when the step S203 is carried out toall the files.

The corresponding chart thus created is provided to a packetingcomponent 377, shown in FIG. 11, together with each of the modules, andis stored in a memory 382 after packetization.

The data from the data converter 375 is packetized into packets having afixed length by the packeting component 377. The packeting component 377assigns individual PIDs to the section headers of all the packetsgenerated. In this embodiment, the first four digits and the last fourdigits are respectively assigned as the PID and the table_id_extensionregion (field) because the module identifiers consist of thedirectory_id and the file_id (a total of eight digits).

In this way, the packets making up each file can definitely be specifiedwithout further consideration in the receiver by distinguishing themusing the PID of each packet and the table_id_extension as a result ofdistinguishing the modules by the PID and the table_id_extension of eachpacket.

Further, the packeting component 377 also packetizes the correspondingchart created by the data converter 375 into packets having a fixedlength. In other words, the corresponding chart is multiplexed as thecorrespondence table 109 depicted in FIG. 4.

There are table_id regions (fields) for setting own table_id, eachhaving a predetermined data length, and table_id_extension regions(fields) for setting own table_id_extensions in the sections heads ofeach packet. Their own module_ids are stored in the table_id_extensionfields as the table_id_extensions. The details of this relationship willbe described later.

A packet multiplex controller 384 reads out the data stored in thememory 382 in response to its encoding speed. Also, the controller 384provides PIDs assigned to the data to a PMT generating circuit 386.

The PMT generating circuit 386 generates a control data PMT 114 (seeFIG. 4) as a result of receiving the PIDs. The PIDs for each packetrelated to contained in the service 1014 are listed in the control dataPMT 114. Both the data thus read out from the memory 382 and thecorresponding control data PMT are stored in a memory 364 in a multiplexformat under a time-sharing manner. Additionally, the PMT 114 containsthe module_id into an additional information field by the circuit 386,the module_id corresponding to an HTML file comprising a front pagedisplayed initially in the service 1014 as shown in FIG 7. In this way,a table_id_extension “0x0001” is written to an additional informationfield in the PMT of the service 1014 as a file_id of the front page whenthe front page is represented by file “¥weather¥forecast.html”, becausethe file “¥weather¥forecast.html” is replaced with a file_id “0001”during the packetization. Also, the file “¥weather¥forecast.html” isreplaced respectively with a PID “0x0001” and a table_id_extension“0x0001” during the packetization.

1-2-2. Receiver

1-2-2-1. Hardware Structure

The hardware structure of the receiver 11 depicted in FIG. 1 is shown inFIG. 19. The receiver 11 functions as a receiver of satellitebroadcasting as well as a device for displaying HTML data on a monitor.

The function of the receiver 11 in receiving satellite broadcasting issimilar to that of the conventional broadcasting receiver, as brieflydescribed below. Radio waves transmitted by the transmitter are caughtwith an antenna 131, and the radio waves are supplied to a tuner 132.The tuner 132 selects one of the transport streams in accordance with acommand of the CPU 147. Further, the tuner 132 carries out demodulationand error-correction and other relevant operations, and outputs theresultant signals to a transport decoder 141.

The transport decoder 141 only selects (i.e., filters) predeterminedpackets out of the packets multiplexed within the selected transportstream in accordance with PIDs set therein by the CPU 147. Packetizeddata for the system are contained in the multiplexed packets other thancontrol data, video data and audio data because the system data are alsomultiplexed together with the video data and the audio data. Thetransport decoder 141 identifies these data in accordance with the datastored in the headers in each of the files, and both the control dataand the system data are stored in a RAM 144. The RAM 144 stores thepacketized data under the file basis so that the packetized data thusstored forms to one independent file.

Filtering procedure carried out in the transport decoder 141 will bedescribed with reference to FIG. 20. Conditions for performing filteringof data (hereinafter referred to as filtering conditions) are stored ina filtering conditions storing unit 154. For example, PIDs, the table_idand table_id_extensions of the packets to be selected are storedtherein. A PID selecting unit 156 selects the packets havingpredetermined PIDs in accordance with the filtering conditions stored inthe filtering conditions storing unit 154. The packets of video data andthat of audio data, are respectively outputted to a video decoder 137and an audio decoder 134. Packets of HTML or image data in a selectionformat with the selected packets are outputted to a section dataselecting unit 155 shown in FIG. 20. The section data selecting unit 155only outputs the packets having predetermined table_id_extensions inaccordance with the filtering conditions stored in the filteringconditions storing unit 154.

A conditions varying unit 153 varies filtering conditions stored in thefiltering conditions storing unit 154 in accordance with a rewritecommand outputted by the CPU 147 as shown in FIG. 19.

The video data are provided to the video decoder 137 through the FIFOmemory 136 depicted in FIG. 19, and are decompressed or expandedthereby. The video data are converted into analog signals with adigital/analog converter (hereinafter referred to as D/A converter) 138,and the analog signals are displayed on a monitor 140 such as a liquidcrystal display, a cathode ray tube and the like through a videosynthesizer 139. The data representing characters stored in a video RAM(hereinafter referred to as VRAM) are converted into analog signals withanother D/A converter 145, and the analog signals are provided to thevideo synthesizer 139. In this way, characters can be overlapped onimages displayed on the monitor.

The audio data, on the contrary, are provided to the audio decoder 134through another FIFO memory 133, and are decompressed or expandedthereby. The audio data are outputted through a speaker 135 as actualsound.

A remote controller 149 stores the following commands such asinitialization of watching, designation of services, instruction forcategory search for the program information or the like, and thecontroller 149 outputs them to a microcomputer 148 installed in the mainpart of the receiver 11.

The CPU 147 controls the tuner 132, the transport decoder 141 andrelevant components in accordance with a receiving operation controlprogram 142 c and a display program 142 a both stored in a ROM 142.These programs may be capable of stand alone operation, or may requirean operating system (such as Windows™ CE by Microsoft™ Inc.) as apremise.

1-2-2-2. Receiving Operation Control Program

An embodiment of the receiving operation control program 142 c used forcarrying out receiving operations will be described with reference toFIG. 19 and FIG. 21. Operations necessary to switch the receiver 11 fromreceiving the service 1013 contained in the transport stream 1010, toreceiving another service 1011 included in the transport stream 1010,will be described herein. A switching command is sent by the remotecontroller 149 or a control panel (not shown) to the CPU 147. Theswitching command is provided to the CPU 147 through a microcomputer 148(as shown in FIG. 19). In response to the switching command, the CPU 147sets PIDs of the control data PAT into a register (not shown) forseparating the control data in the transport decoder 141. The PID of thecontrol data PAT has a fixed value such as “0x0000”. In this way,contents of the control data PAT being separated are stored in the RAM144 under the control of the transport decoder 141 (step S11, in FIG.21). A list of the services multiplexed in the transport streamcurrently received are shown in the contents of the control data PAT(see FIG. 8). The CPU 147 determines that the desired service 1011 ismultiplexed in the transport stream 1010 currently received by referringthe list. The CPU 147 continues processing from step S12 to step S18.

In the step S18, the CPU 147 obtains PIDs of the control data PMT in thedesired service 1011 in accordance with the contents of the control dataPAT. As a result, the CPU 147 recognizes that id “0x0011” is for a PIDof the control data PMT in the desired service 1011 as shown in FIG. 8.Further, the CPU 147 sets the PID “0x0011” of the control data PMT intothe register for separating the control data in the transport decoder141 (step S19). Hence, the control data PMT 111 in the service 1011 canbe separated from other data, and contents of which can be stored in theRAM 144.

Next, the CPU 147 recognizes PIDs “0x0022” and “0x0024” of the videodata 81V and the audio data 81A respectively, in accordance with the PMTfor the service 1011 as shown in FIG. 6 (step S20).

Then, the CPU 147 sets both the PIDs “0x0022” and “0x0024” into thefiltering conditions storing unit 154 (see FIG. 20) in the transportdecoder 141 (step S22). In this way, the transport decoder 141 canselectively output both the video data 81V and the audio data 81A, bothbeing required.

The CPU 147 proceeds its processing to step S13 if the desired serviceis not multiplexed in the transport stream currently received in stepS12. Further, the CPU 147 obtains PIDs of the control data NIT assignedin the control data PAT. In accordance with the PIDs thus obtained, theCPU 147 obtains the control data NIT, and determines whether the desiredservice contained in any of the transport streams (step S14, step S15).

The CPU 147 switches a setting of the tuner 34 so as to receive thetransport stream which contains the desired service (step S16). Then,the CPU 147 obtains the control data PAT of the transport stream (stepS17). Hereafter, steps following to step S18 may be performed, asdescribed above.

1-2-2-3. Display Program

The function for displaying HTML data on the monitor is accomplished bythe CPU 147 and the display program 142 a stored in the ROM 142.

Data obtained is stored in the RAM 144 when the data is system dataunder the control of the transport decoder 141. The CPU 147 startsperforming the display program 142 a when the system data is supplied bythe transport decoder 141 because the CPU 147 recognizes data written ina section format as system data in this embodiment.

Steps performed by the display program 142 a for displaying HTML fileswill be described with reference to FIG. 19 and FIG. 22.

At first, a switching command, for switching the operations to a servicein which the HTML files are received, is outputted by the remotecontroller 149 in accordance with input of the operator who refers aprogram table. As a result of receiving the command, the CPU 147 variesfiltering conditions in the tuner 132 and the transport decoder 141respectively.

For example, the operator selects a service id=“001” with the remotecontroller 149 when he/she find out a weather forecast which providesinteractive service can be specified by the service id=“001” byreferring to the program table.

Control data PAT is obtained by varying the filtering conditions of thetransport decoder 141 to PID=“0x0000” with the CPU 147 because the PIDof the PAT is a fixed value “0x0000”. Steps for obtaining the controldata PAT are performed after switching the tuner 132 so as to receive atransport stream in which a service specified by the service id=“001” ismultiplexed as a result of obtaining the control data NIT thereof whenthe service having the service id=“001” is multiplexed in the transportstream other than the transport stream currently received.

A PMT of the service specified by the service id=“001” can be obtainedonce the control data PAT is obtained. As a result of obtaining the PMT,an id of the transport stream in which the service is multiplexed, PIDsof packets in which data related to the service is stored, andtable_id_extensions of the file which are displayed at first canautomatically be obtained. Under this logic, the CPU 147 variesfiltering conditions in the transport decoder 141 while switching thetuner 132 in order to receive the service. In this way, receipt of aservice specified by a service id “001” is started.

For instance, the CPU 147 varies filtering conditions in the transportdecoder 141 so as to select packets of a PID “0x0001”, that of atable_id “0x3C”, and that of a table_id_extension “0x0001” shown in FIG.23A when the PID, the table_id, and the table_id_extension of theservice specified by the service id=“001” are respectively “0x0001”,“0x3C”, and “0x0001” according to the PMT. The table_id is a fixed valueof “0x3C”. Further, the numbers “0x” means that the numbers followingthereto are expressed in hexadecimal in this embodiment.

Consequently, the transport decoder 141 selects the packets having theirPIDs, table_id, and table_id_extension as “0x0001”, “0x3C”, and “0x0001”respectively. Selective reception of the HTML files shown in FIG. 13Aaccording to the filtering conditions will be described below as anexample.

The CPU 147 judges whether or not the system data stored in the RAM 144comes to one independent file (step S101, in FIG. 22). In a concreteform, the judgement can be carried out by detecting whether or not thelast block of the system data is received. The counter i is initializedonce the one independent file is received (step S103). The CPU 147detects existence of an automatic reference tag in the HTML data of thefile located in i th row thereof (step S105). The automatic referencetag is defined as image tags for referring other file(s) regardless ofthe operations by the operator. Operations related to the automaticreference tag will be described later. Since the counter i was initiallyset to 0, the first time CPU 147 executes step S105, it will move ontostep Sill and generate display data according to the data located in thei th row. The display data is stored to a VRAM 146, then converted intoanalog data by the D/A converter 145. After conversion to analog data,the display data is provided to the video synthesizer 139. The videosynthesizer 139 outputs display data which is synthesized with the datafrom the video decoder 137 thereby to the monitor 140. Hence, a imageaccording to the data located i th row is displayed on the monitor 140.

Next, the CPU 147 increments the counter i by one (step S113), andjudges whether or not a tag “</html>” is assigned to the i th row (stepS115). The CPU 147 repeats steps following to step S105. In this way,images according to data located each of the rows are displayedsequentially on the monitor 140 (see FIG. 19).

An image such as that shown in FIG. 14A is displayed on the monitor 140when the tag “</html>” is assigned to the i th row that forms the lastrow in step S115. The operator operates the remote controller 149 toobtain detailed information which the operator desires during thedisplay of such image. For example, the CPU 147 resets the filteringconditions in step S117 in FIG. 22 as a result of making a judgment thatthe reference command(s) for referring other file(s) is provided theretowhen the operator selects detailed information of “1. Today's weather”(step S119).

In a concrete form, the CPU 147 varies the filtering conditions so as toselect a file “¥weather¥today.html” in accordance with the source codesshown in FIG. 13A when the operator selects a region displaying theinformation of “1. Today's weather” by the remote controller.Practically, the filtering conditions are varied as described below. TheCPU 147 obtains a module identifier of the file specified by“¥weather¥today.html” by referring to the correspondence table depictedin FIG. 15. In this case, assignment of PID “0001” to the file“¥weather¥today.html” is recognized by the CPU 147, and the file havinga table_id_extension “0x0002” assigned to its section header istransmitted. Therefore, the filtering conditions for the transportdecoder 141 are set so as to selectively receive packets having atable_id_extension “0x0002” from the conditions to receive the packetshaving a table_id_extension “0x0001” as shown in FIG. 23B. In this way,packets having the table_id_extension “0x0002” can be received. Novariation is required to the PID because it remains the same.

Thereafter, another image shown in FIG. 14B is displayed on the monitor140 according to the HTML file depicted in FIG. 13B by performing stepsfollowing to step S101 repeatedly.

Hence, a file(s) required for displaying desired image(s) can bereceived at each time desired and is displayed by actively varying thefiltering conditions in the transport decoder 141. In this way, it isnot necessary to store all the files for the display once in the storingpart as in the conventional art.

Another image, according to the HTML file depicted in FIG. 13C which isselectively received in accordance with the filtering conditions shownin FIG. 23C, is displayed when the operator selects “OSAKA” during thedisplay of the image shown in FIG. 14B. An <img src> tag as theautomatic reference tag is assigned in the HTML file thus received. As aresult, the CPU 147 performs a series of steps from step S107 to stepS109 in FIG. 22 according to the row in which the tag is located. Thefunctions performed in step S109 and step S107 are the same as step S101and step S119 respectively.

The CPU 147 additionally sets filtering conditions for the transportdecoder 141 so as to select a desired HTML file(s) when it detectsexistence of the automatic reference tag in the HTML file(s) in stepS105. In a concrete form, it is preferred to select another filespecified by “0001/1000.gif” in addition to the HTML file shown in FIG.13C because a plurality of conditions may be set as the filteringconditions for the transport decoder 141. The filtering conditions forthe transport decoder 141 are set so as to selectively receive packetshaving a table_id_extension “0x1000”.

Data in the received packets is temporarily stored in the RAM 144, andthe CPU 147 outputs a display command according to the stored data. Thedata thus stored is displayed on the monitor 140 in accordance with thedisplay command.

As described above, HTML files are transmitted repeatedly from thetransmitter, and the files are received by the receiver when they areneeded for reference, in this embodiment. In this way, the display ofinformation can be switched dynamically by selectively receiving thefiles required solely at the receiver without storing all the HTML fileseven on a temporary basis.

Further, selection of the packets is performed by using a filteringfunction of the transport decoder 141. Thus, the CPU 147 may vary thefiltering conditions in the transport decoder 141 by referring thecorrespondence table being received. Thus, only the packets contained inthe files which are required to be referred need be extracted.

In addition, the filtering conditions can also be varied quickly evenwhen an automatic reference tag(s) is assigned in the files. In thisway, the files required can be displayed quickly.

Hence, the following procedures are performed within/between thetransmitter and the receiver respectively in this embodiment. Thetransmitter transmits the correspondence table created thereby, whilevarying the name of each HTML file in accordance with the table. Also,the receiver receives the table transmitted by the transmitter andstores the table therein, and the receiver varies filtering conditionsin the transport decoder by specifying the required file(s) with the CPUin accordance with the table. In this way, display of the HTML datatransmitted via satellite broadcasting can be carried out according tointeractive operations even when the receiver has a capability ofstoring just the required file(s).

1-3. Second Embodiment

In the first embodiment, the filtering conditions in the transportdecoder 141 are varied by referring the correspondence table shown inFIG. 15 with the CPU 147. On the contrary, the second embodiment willdisclose a data communication system capable of actively receivingpackets consisting of a desired file(s) without transmitting thecorrespondence table. Instead, in this embodiment HTML data which areautomatically changed their file names and transmitted thecorrespondence table.

1-3-1. Data Converting Operations in Transmitter

Data converting operations performed by the transmitter will bedescribed hereunder. The hardware structure of the transmitter isidentical with that of the transmitter described in the firstembodiment. In this embodiment, the data converter 375 shown in FIG. 11changes file names of the HTML data into individual module_ids describedin the first embodiment.

For example, file names shown in FIG. 12 are changed into four digitnumerals expressed in hexadecimal which can directly be selected by thetransport decoder as shown in FIG. 24. File names“¥weather¥forecast.html”, “¥weather¥today.html”, . . . are changedrespectively into “/0001/0001.html”, “/0001/0002.html” . . . in turn.Further, file names to be referred in each of the HTML source files arechanged so as to correspond the new file names. For example, a file name“¥weather¥today.html” is changed into “0001/0001.html” in the tag <Ahref/weather> as shown in FIG. 25A.

The data converter 375 is realized by a software structure using a CPUin this embodiment. Detailed description of the data converter 375hardware structure is omitted hereunder because the hardware structureof the data converter 375 is identical to that used in the firstembodiment. Steps performed in a program for conversion used by the CPU375 c will be described with reference to FIG. 16 and FIG. 26.

The CPU 375 c initializes two counters i and j (step S301, in FIG. 26).Then, the file corresponding to the counter i is stored into thecorresponding chart (step S303). The function performed in step S303 isthe same as that carried out at step S203, in FIG. 18. Next, the CPU 375c changes a file name of the file located in i th row into a module name(step S305). For instance, the file name “¥weather¥forecast.html” ischanged into the module name “/0001/0001.html”.

Next, the CPU 375 c determines whether or not all the file names arechanged into modules names (step S307), increments the counter i by oneif all the file names are not changed (step S309), and stores the nextfile in the corresponding chart (step S303). Change in file contentsdata of the file located in j th file in the correspondence table isperformed by using the correspondence table (step S311) after the stepsperformed in step S303 and step S305 are carried out to all the files.

Next, the CPU 375 c determines whether or not these steps are carriedout to all the files (step S313), increments the counter j by one ifthese steps are not carried out to all the files (step S315), andchanges the file data. Thus, after finishing step S311 to all the files,the data converting operations performed automatically are completed.

The corresponding chart thus created, is provided to the packetingcomponent 377 shown in FIG. 11 together with each of the modules, and isstored in the memory 382 after packetization.

As described above, HTML files are transmitted repeatedly from thetransmitter, and the files are received by the receiver when they areneeded for reference, in this embodiment. In the transmitter, the moduleidentifier assigned to each of headers are formed in character stringswhich can directly be recognized by the transport decoder so as toselect each of the HTML files. A desired HTML file(s) is extracted byvarying the filtering conditions according to the module identifier inthe receiver. In this way, the display of information can be switcheddynamically by selectively receiving the files required solely at thereceiver without storing all the HTML files even on a temporary basis.Therefore, the files required can be displayed quickly.

In addition, the filtering conditions can also be varied quickly evenwhen an automatic reference tag(s) is assigned in the files. In thisway, only the files required can be displayed quickly.

1-3-2. Data Receiving Operations in Receiver

Detail description of the receiver is omitted hereunder because thehardware structure of the receiver is identical to that used in thefirst embodiment. In this embodiment, both the file names (absolutepath) and the file names to be referenced are changed into the filenames which can directly be recognized by the transport decoder. It is,therefore, not necessary for the receiver to refer the correspondencetable. In this way, display according to a desired HTML file(s) can becarried out without giving too much load to the CPU as well as notstoring all the HTML files in the receiver even when a plurality of HTMLfiles are linked thereamong.

In order to apply the display program shown in FIG. 22 to the receiver,the step carried out at step S119 may be amended as follows. Forexample, the CPU 147 varies the filtering conditions according to thesource codes shown in FIG. 25A so as to select a file “0001/0002.html”when the operator selects a region on which “1. Today's weather” isdisplayed by using the remote controller. The variation of the filteringconditions may be carried out in similar manner to that of the firstembodiment such that the table_id_extension “0x0001” is varied to thetable_id_extension “0x0002”. No variation is required to the PID becauseit remains the same.

In this embodiment, each of the files is indicated in a full path formatby adding a symbol “/” indicating a directory in which the file belongstherein. For example, the file “0001.html” in a directory “/0001” isindicated as “/0001/00001.html”.

In this embodiment the desired HTML file(s) can be extracted by varyingthe filtering conditions in the receiver without using thecorrespondence table because identifiers of the HTML files are specifiedby numbers which can directly be recognized by the transport decoder.Therefore, all the desired data can be displayed quickly.

Further, each of the files belonging to a directory having the name of“¥weather” is described in this embodiment. Each of the files candefinitely be specified by distinguishing the name of the directory andthe relative path using the PID and the table_id_extension respectively.The specification of the files is not limited by that way, it can becarried out by applying plural number of module identifiers in turnwhich are prepared as the correspondence table shown in FIG. 17A inwhich each module identifier has different directory name when aplurality of files belong to different directories. Further, it can alsobe performed by applying the module identifier having the same directoryname.

In addition, a module identifier having different directory name may beadded even when a plurality of files belong to the same directory. Thisis advantageous because image data can be specified by just using PIDswhen one of image data contained in a specific service is free ofcharge, and another image data in the service may be charged under acertain rate. In this way, the chargeable data can be distinguished fromthe data free of charge by referring PIDs. For example, in the case ofdefining data to be charged or free of charge such that from data“sport1. html” through data “sport9. html” are free of charge, and fromdata “spoort10. html” through data “sport29. html” are chargeable, thesedata are divide into two different groups in accordance with their PIDs.By grouping into two different groups such as a first data group consistof data “sport1. html” through data “sport9. html” which belong to thedirectory “0001” and a second data group formed of data “spoort10. html”through data “sport29. html” which belong to the directory “0002”, onlythe data having their PIDs of 0002 can be charged under a certain rate.

1-4. Third Embodiment

FIG. 27 is a block diagram showing an overall structure of a digitalbroadcasting system to be used in a third embodiment of the presentinvention. The system comprises a data transmitter 410 and a datareceiver 414.

1-4-1. Data Transmitter

The data transmitter 410 includes a data storing part 411, a dataconverting part 412, and a data multiplexing and transmitting part 413.

The storing part 411 is composed of a storing device e.g., a hard diskor an optical disk filing device, for storing digitized data therein.All the data are made correspondently so as to be distinguished oneanother without further consideration by their file names.

The converting part 412 converts data read out from the storing part 411into down-load data block (hereinafter referred to as DDB) sectionswhich are capable of being transmitted under the DSM-CC Data Carouselused as a protocol in an MPEG-2 transport stream. In a concrete form,the converting part 412 defines module_id which are specified by thefile names stored in the storing part 411 into table_id_extension fieldsof section headers when the data is converted into the DDB sections.Further, the converting part 412 repeatedly outputs the converted datato the data multiplexing and transmitting part 413 so as to multiplexthem thereby using the PIDs specified in accordance with the file names.The module_id are indicated in four digits in hexadecimal because thefile names are expressed in the same manners.

FIG. 28A shows a structure of the data stored in the storing part 411.The file name of directory data 530 is “/0001” when it is expressed in afull path format. The directory data 530 includes a list of filescontained in the directory, in this case, files “0001.html”,“0002.html”, and “0003.html” are in the data 530. File names of thefiles “0001.html” and “0002.html”, and “0003.html” are expressedrespectively in a full path format of “/0001/0001. html”,“/0001/0002.html”, and “/0001/0003.html”. The file “/0001/0001.html” isHTML data having a row 532 requiring reference of a file“/0001/0002.html” and another row 533 requiring reference of a file“/0001/0003.html”.

The files “/0001/0002.html” and “/0001/0003.html” are HTML files havingdata 534 and 535 respectively.

FIG. 28B shows a data structure of each module for outputting thedirectory data and the file data shown in FIG. 28A. In this embodiment,each of the output data is transmitted as U—U object because the DSM-CCstandard is employed in this embodiment. The U—U object in the DSM-CCstandard is defined as data in which object headers are assigned toeither of the directory data or the file data.

In the FIG. 28B, a directory object 536 is a module including thedirectory data 530 and having module_id “0000”. Similarly, file object537 is a module including the HTML file data 531 and having module_id“0001”. Further, another file object 538 is a module including the HTMLfile data 534 and having module_id “0002”. Still further, another fileobject 539 is a module including the HTML file data 536 and havingmodule_id “0003”.

FIG. 29 shows a data hierarchy of a DDB section when the DDB section isdefined as a k th block as a result of dividing a module formed byassigning an object header to the file data 535 having module_id “0003”into “n” blocks.

In order to carry out filtering of sections with the hardware, one U—Uobject is transmitted as one broadcast inter-ORB protocol (BIOP) messagein this embodiment. Each module is divided into a plurality of blockseach having a fixed size (only the last block may be less than the fixedsize), and the divided modules are repeatedly transmitted as DDBmessages.

The DSM-CC standard further defines a format of transmission on theMPEG-2 transport stream. In order to easily realize the filtering insection at the receiver, a table_id and a table_id_extension areassigned to a header of the DDB section.

Next, data converting operations performed by the data converter 412shown in FIG. 27 will be described hereunder. The DDB section includes asection header field and a DDB message field. The section header fieldhas a table_id field storing a table_id of 8 bits and atable_id_extension field storing a table_id_extension of 16 bits. Blockdata dividing the file object 539 shown in FIG. 28B into a predeterminedlength (each having 4066 bites) are stored in the DDB message field.

Data “0x3C” is set into the table_id field because the table_id of theDDB section is defined as “0x3C”, data “0003” forming a module_id of theobject is set in the table_id_extension field.

Further, name of the files consisting the modules indicated in the fullpath format is specified by eight digits in hexadecimal in thisembodiment. The data converter 412 assigns the last four digits(equivalent to data of 16 bits) to the table_id_extension field becausethe field is only capable of storing data of 16 bits. At that time, thedata converter 412 outputs a command for multiplexing the first fourdigits by using its PID to the data multiplexing and transmitting part413. For example, a file “/0001/0003.html” stored in the storing part411 is packetized as a file having its PID “0001” and itstable_id_extension “0003”.

The data multiplexing and transmitting part 413 multiplexes a programallocation table (PAT) and a program map table (PMT) both defined by theMPEG-2 system, service information defined by the digital videobroadcasting specification for service information (DVB-SI) standard, anaudio video (AV) stream encoded under MPEG-2, a download informationindication (DII) section defined by the DSM-CC standard all of which arenot shown as input thereto, and a plurality of DDB sections outputted bythe data converter 412 by using PIDs specified. And the datamultiplexing and transmitting part 413 encodes the multiplexed data inresponse to the transmission path being used. In a concrete form, achannel code processing is performed as a channel coding method. Forexample, the method includes random processing, error correctingprocessing, and interleave processing. Thereafter, stream data obtainedas a result of performing a modulation in digital format such as 64quadrature amplitude modulation (QAM) is transmitted as radio waves.

In this way, the data transmitter 410 can transmit packetized HTML filesrepeatedly.

1-4-2. Data Receiver

Next, the structure and operations of the data receiver 414 depicted inFIG. 27 will be described hereunder. The data receiver 414 comprises afiltering part 415, a primary storing part 416 which stores variousdata, a filtering conditions varying part 417, and a file obtainingcommand part 418.

The filtering part 415 receives a desired transport stream out of thestreams transmitted thereto as radio waves. Section data having exactmatch with the filtering conditioned being specified in the filteringpart 415 is stored in the primary storing part 416. The filtering part415 extracts only the packets having the specified PIDs and the packetsin which both table_id and table_id_extension are defined out of thereceived transport stream.

The primary storing part 416 may be realized with a RAM, and it storesdata being extracted by the filtering part 415.

The filtering conditions varying part 417 varies the filteringconditions stored in the filtering part 415 so as to extract the desiredHTML file(s) in accordance with input of the operator.

A data processing part 419, an input part 420, and a display part 421are included in the file obtaining command part 418.

The data processing part 419 generates images for displaying on a screenof the display part 421 as a result of performing data processing ofmultimedia data such as HTML data, bit map data or audio/video data.Also, the data processing part 419 performs data processing inaccordance with a command signal outputted by the input part 420, andrevises the images generated thereby as a result of the data processing.Further, the data processing part 419 outputs a command for varying thefiltering conditions which includes name of a desired file to thefiltering conditions varying part 417 when another file is required as aresult of performing the data processing.

The input part 420 sends signals in response to the inputs of theoperator to the data processing part 419.

The display part 421 displays the images generated by the dataprocessing part 419 on its screen.

Next, functions of the filtering conditions varying part 417 installedin the data receiver are outlined with reference to FIG. 30. As shown inFIG. 30, the file name is composed of a PID and a module_id botharranged sequentially by using symbols “/” and “.” as delimiters, eachof the PID and the module_id being indicated adjacently into four digitnumerals expressed in hexadecimal. For instance, data “0001” and “0003”respectively indicate a PID and a module_id in a file name“/0001/0003.html” specified by the file obtaining command part 418.

The filtering conditions varying part 417 depicted in FIG. 27 extracts aPID and a module_id out of the file name, and converts them into thefiltering conditions shown in FIG. 30. The numbers except for both thePID and the module_id are fixed numbers. Upon setting the filteringconditions in the filtering part 415, sections, having their values of atable_id and that of table_id_extension field which are set in a maskbit of the section header as 1, both respectively “0x3C” and “0003” outof the packets being transmitted that have their PID “001”, are storedin the primary storing part 416 by using the filtering function of thetransport decoder. All the data contained in the file “/0001/0003.html”which is transmitted as the DDB sections can be obtained by setting thefiltering conditions.

Sections consisting one complete file can positively be selected byreferring their section numbers because section numbers of the sectionsand number of the last section are stored in the section header of eachsection.

The decision for determining whether or not blocks are part of a certainmodule is made by carrying out the following steps. The number of thelast section in the module is stored in the section headers of the DDBsection. Blocks, until one of which has the same number as the lastsection number, can be recognized as one complete module. However, thereis a case that one module possibly consist of more than a total of 256blocks which is defined as the maximum number for one module expressedin 8 bits when a specific module contains a large amount of data becausethe last section number is expressed in 8 bits. In such a case, thedecision for determining the last blocks in the module can not be madebecause the section number of the DDB section take another round. Inthat case, one can make a decision that the blocks having sectionnumbers more than 256 are also part of the module as a result ofcounting the section number.

1-4-3. Hardware Structure of Data Receiver

Next, the hardware structure of the data receiver 414 realized by usinga CPU, is shown in FIG. 31. The data receiver 414 comprises a tuner 640,a transport decoder 641, an audio video (AV) decoder 642, an inputinterface (I/F) 643, the CPU 644, a ROM 645, and a RAM 646.

The tuner 640 selects a transport stream out of the radio waves inaccordance with a command from the CPU 644, and pass the stream to thetransport decoder 641. The transport decoder 641 selects section datahaving exact match with the filtering conditions being specified withinthe transport stream thus received in accordance with a command from theCPU 644. The section data thus selected is sent to the RAM 646, andstored therein. In this embodiment, the transport decoder 641 and thetuner 640 function as the filtering part 415.

Further, the transport decoder 641 sends PES packets of audio/video datacontained in the transport stream received under the command from theCPU 644 to the AV decoder 642, the audio/video data having the specifiedPIDs. The AV decoder 642 decodes the audio/video data thus received, andoutputs images and sounds. Further, the AV decoder 642 synthesizesgraphic data of on-screen display (OSD) under the command from the CPU644, and outputs the graphic data thus synthesized as images. Theoutputs of audio/video from the AV decoder 642 are provided to TVmonitor and the like which displays the images under the NTSC system orthe PAL system.

The input interface (I/F) 643, comprising an infrared detector and thelike, receives input signals outputted by the remote controller.

The CPU 644 controls other hardware in accordance with a program storedin the ROM 645.

The filtering conditions varying part 417 is realized by the AV decoder642, the input I/F 643 and the program stored in the ROM 645.

The ROM 645 stores all the programs for controlling the data receiver414. The RAM 646 is used for performing the programs stored in the ROM645 with the CPU 644. Further, the RAM 646 stores the data filtered bythe transport decoder 641 therein.

FIG. 32 is an overall view of a communication system using the datareceiver 414 depicted in FIG. 31 as receiver system. In thecommunication system, a data receiver 651 is connected with both anantenna 650 and a television (TV) monitor 653 as shown in FIG. 32. Aselection command is provided to the data receiver 651 in response tothe input of the operator into a remote controller 652.

Data display on the TV monitor 653 will be described hereunder. Databeing processed from the HTML data 531 shown in FIG. 28A is displayed onthe TV monitor 653 as graphic data of on-screen display.

Both the characters “Chapter 1” and “Chapter 2”, each containedrespectively in the row 532 and the row 533 in FIG. 28A, arerespectively displayed on a region 654 and a region 655 on the TVmonitor 653. The display is called as a hot-spot. In this example, theregion 655 is a region currently selected, and is highlighted. Thisstate is referred to as a selected status of the hot-spot.

The CPU varies filtering conditions in the transport decoder 641 so asto extract the file “/0001/0003.html” when the operator inputs a command“SET” as a result of making a decision that the file “/0001/0003.html”is need to be referred.

As described earlier, the file data can selectively be divided by usingthe transport decoder in the filtering part 415. The divided file dataare stored directly in the primary storing part by providing the dataconverter 412 and the filtering conditions varying part 417 respectivelyto the data transmitter and the data receiver in this embodiment.

Although, the files being transmitted are HTML files in the embodimentsdescribed earlier, other data may be used instead of the HTML files.

In the system according to the present invention, data of the desiredfiles(s) can directly be obtained in the primary storing part from thetransmitted data at the data receiver without using a secondary storingpart by providing the data converter and the filtering conditionsvariation part respectively to the data transmitter and the datareceiver, the data converter being operated to convert the file name(s)into data to be recognized by values converted in accordance with acertain rule, and the filtering conditions variation part being operatedto convert the file name(s) into filtering conditions in accordance witha certain rule.

Further, it is not necessary for the receiver to refer thecorrespondence table for varying the filtering conditions in thetransport decoder. It is, therefore, possible to provide a receiver forbroadcasting capable of decreasing the amount of calculation performedby the CPU as well as saving its data storing capacity.

1-5. Fourth Embodiment

In each of the embodiments described earlier, file names of the filesare changed into a certain number of digits and a certain kind ofcharacters capable of reading the transport decoder, and the file namesare assigned to each of the packets as module_id. In other words, themodule_id are uniquely assigned to each of the packets. In thisembodiment, however, the same module_id are assigned to a plurality offiles having a certain relationship thereamong.

For example, a reference file “sample.html” shown in FIG. 33 is htmldata which defines positions of three referred files such as files “s1.png”, “s2. gif”, and “s3. jpeg” in the display by style tags. In thisway, a video image shown in FIG. 34 is displayed on the TV monitor andthe like.

The filtering conditions of rows containing these referred files “s1.png”, “s2. gif”, and “s3. jpeg” are varied upon reading the rows. Itmight take a certain period of time to display the images when thevariation of the filtering conditions is performed at an inappropriatetiming because each of the packets containing identical data isrepeatedly transmitted within a certain period.

In order to solve the drawback, the same module_id are assigned to thefiles “s1. png”, “s2. gif”, and “s3. jpeg” these having a certainrelationship thereamong, and these files are transmitted. Then, thesefiles are selectively received by using the module_id thus assignedthereto. In this way, all the referred files which will be receivedlater can be received with the reference file(s) thereof as one unitizedfile so that these files can be displayed quickly.

Steps performed in both the transmitter and the receiver, in order toobtain the files in the above manners, will be described. Both thereference file and the referred files are stored in the same directoryin the transmitter as shown in FIG. 35. The name of the directory can bedefined as a name using a certain number of digits, or a certain kindsof characters, and can be read by the transport decoder. In thisembodiment, the module_id is used as the directory name unlike in thesecond embodiment in which the file name is assigned as the module_idwhen the files are packetized. In other words, the same module_id “0001”are assigned to the packets consisting the files “s1. png”, “s2. gif”,and “s3. jpeg”, and then the packets are transmitted. In order tospecify the directory name, for example, the following procedure isperformed such that only the directory name is converted into a certainkind of characters having a certain number of digits capable of readingby the transport decoder so that the receiver may determine which datashould be specified as the module_id. The directory name may also bespecified by judging a part located between “/” being put before thefile name and “/” being put thereafter, and the data existingtherebetween may also be specified as its module_id.

In order to select a file(s) with the receiver, all the file(s) havingthe same id are selectively received thereby and are temporarily storedin a cache memory having a ceratin capacity and prepared in the RAM 144.The CPU may conduct a search to find a referred file when reference isneeded.

FIG. 36 is a flow chart for describing steps for displaying images inthe receiver. One noticeable difference between the steps in the FIG. 22and that in this embodiment is that the CPU detects existence of thereferred file within the cache memory in step S106 after detectingexistence of the automatic reference tag in step S105. Anothernoticeable difference therebetween is that the directory name of thefile is set to the transport decoder as the filtering conditions in stepS107 when no existence of the referred file within the cache memory isdetected in the previous step. For example, directory name 0001 in which“s1.png” is included is set to the transport decoder as filteringconditions of the row where a file src=“http://www/dirA/0001/s1.png” islocated thereon. In this way, packets of other files “s2.gif”, “s3.jpeg”can also be stored in the cache memory.

Similar steps to both steps S106 and S107 are carried out in steps S118and S119 such that the CPU detects existence of the referred file withinthe cache memory, and then the directory name of the file is set to thetransport decoder as the filtering conditions when no existence of thereferred file within the cache memory is detected in the previous step.

Alternatively, both the reference file and the referred file may betransmitted as one unitized file. For example, a definition“multipart/mixed” which indicates the file thus defined consisting of aplurality of files, is allowed in the html format. Under thecircumstance, files depicted in FIG. 35 may be transmitted as oneunitized file shown in FIG. 37 and FIG. 38. In this way, both thereference file and the referred file can be received at the same time,so that these files can be displayed quickly.

On a row 611 in FIG. 37 is a specification statement which declares thefile consist of a plurality of files connected in series. Another row615 shows a delimiter of the files connected in series. In other words,“boundary=“boundary-sample” itself forms the delimiter to the filelocated therebefore and thereafter in this case. Another row 621 shows afile name, and yet another row 623 describes a data length such as 928bytes. Another row 619 shows a data format of the file, that is textdata in the html format. Another row 613 describes both a directory inwhich the file is contained, and a computer storing the directorytherein.

Further, rows 627, 629 indicate contents of the first file“sample.html”.

In addition, a row 630 contains data related with the second file“s1.png”, rows 631, 633, 635, 637, and 639, respectively shows adelimiter, a data format of the file, a file name, a data length, andcontents of the second file. In this case, the second file is formed byimage data in the png format.

Both rows 633 and 635, respectively, show regions related with files“s21.gif” and “s3.jpeg”.

Hence, files related one another can be displayed quickly as a result oftransmitting these file connected in series as one unitized file.

While, existence of the automatic reference tag(s) in which no operationis required by the operator is detected in this embodiment, furtherquick display can be carried out by previously selecting referred filewhich need to be inputted by the operator in addition to the automaticreference tag(s).

For example, not only the referred files which need to be inputted bythe operator, but also the automatic reference tag(s) are indicated inthe reference file shown in FIG. 39. In a concrete form, images shown inFIG. 40 are displayed in accordance with the reference file depicted inFIG. 39. An image shown in FIG. 42A is displayed in the case of matchingthe contents of a reference file “t1.html” specified by a row 651 inFIG. 39 with that of an html data depicted in FIG. 41A when the operatorselects a region where an image 641 is displayed thereon shown in FIG.40. Similarly, another image shown in FIG. 42B is displayed in the caseof matching the contents of a reference file “t2.html” specified by arow 653 in FIG. 39 with that of an html data depicted in FIG. 41A whenthe operator selects a region where an image 643 is displayed thereonshown in FIG. 40.

Similarly, selective reception may be carried out by transmitting files“t1.png”, “t1.html”, “t2.png”, “t2.html”, and “t3.png”, these having acertain relationship thereamong by assigning the same module_id thereto,and receiving them by using the module_id. Hence, not only the referredfiles which will be received later with the automatic reference tag(s),but also other files not specified by the automatic reference tag(s) mayalso be received, so that these files can be displayed quickly.

Although, all the reference files and all the referred files aretransmitted as one unitized file in this embodiment, a quick display maybe realized as a result of omitting variation of the filteringconditions for every row by assigning the same module_id to both areference file and the referred files and transmitting them when thereference file contains a plurality of the referred files.Alternatively, the transmitter may decide whether or not to provide adifferent module_id to the referred files in accordance with frequencyin reference of the referred files.

The same module_id is assigned respectively to the reference file andthe referred files, both stored in the same directory and transmittedwith the module_id in this embodiment. The same module_id is alsoassigned respectively to the reference file and the referred files evenwhen the referred files are stored in a different directory from thatstoring the reference file.

Files “u1.png” and “u2.png”, both belonging to a directoryhttp://www/dirA/0001 which stores a reference file “index._html” asshown in FIG. 45, are stored in the cache memory when the filteringconditions are set so as to selectively receive the reference file“index. html”. In this way, the file “u1.png” can be displayed uponreading the row src=“http://www/dirA/0001/u1.png” without varying thefiltering conditions. In order to distinguishably receive a plurality offiles, a plurality of filtering conditions each having a differentcondition may be set to the transport decoder for each of the files,similar to the case in which packets having a plurality of module_idsare received as one unitized file.

A program for storing data described in FIG. 46, is stored in the ROM142 shown in FIG. 19, and the program is executed in this embodiment.FIG. 46 is a detailed flow chart for describing the step of storing datainto the cache memory.

Steps for displaying data according to a reference file “index.html”depicted in FIG. 44, will be described hereunder. As shown in FIG. 47,the reference file “index.html” is transmitted as a plurality of packetsunder a section basis at the transmission phase. In this case, file id,not module_id, may be transmitted as the second item of the DDB messagesimilar to the conventional manner.

The reason of transmitting the file_id will be described hereunder. Asdescribed earlier, file names are used instead of module_id in the thirdembodiment. Therefore, each of the files can be distinguished by storingthe module_id uniquely assigned to each module, as the second item ofthe DDB message as shown in FIG. 29. In this embodiment, however, thesame module_id are assigned to all the files belonging to a directory.In this way, the receiver can not distinguish every file when no file idare assigned to the packets.

Next, steps for storing data in the cache memory will be described withreference to FIG. 46. The CPU 147 sets filtering conditions for thetransport decoder 141 so as to selectively receive packets having theirtable id extension value of “0001”. The CPU 147 judges whether or not itreceives data from the transport decoder 141 (FIG. 46, step S401), andthe CPU 147 reads out a file name in the DDB message when it receivesdata from the transport decoder 141 (FIG. 46, step S403).

Thereafter, the CPU 147 detects existence of files having the file namereceived from the transport decoder 141 within the cache memory (FIG.37, S405). A file “http://www/dirA/0001/index.html” is stored in thecache memory, because none of such file has been previously storedtherein (step S407). Steps following to step S401 will be repeatedlyperformed.

On the contrary, the file “http://www/dirA/0001/index.html” is linkedwith the data which has already been stored in the cache memory when theCPU finds existence of the file therein because the file has a file nameidentical with that of the file received from the transport decoder 141(step S409).

The CPU 147 judges whether or not all the blocks of the file are stored(step S411), steps following to step S401 will be repeatedly performeduntil all the blocks of the file are stored, signaling completion ofreceiving the file (step S413). On the other hand, steps following tostep S401 will be repeatedly performed as an incomplete of receiving thefile. Files can be stored in the cache memory in the receiver under afile basis even when the same module_id are assigned to a plurality offiles.

As described earlier, each of the files is multiplexed and repeatedlytransmitted in a time-sharing manner by the transmitter. In this way,files such as “http://www/dirA/0001/u1.png”, and“http://www/dirA/0001/u2.png”, both belonging to the same directory areoutputted by the transport decoder 141 when the filtering conditions setin the decoder are “0001”. These data outputted by the transport decoder141 are also stored in the cache memory under the control of the CPU 147according to the steps shown in the flow chart depicted in FIG. 46.

As a result of the data storing, all the files belonging to thedirectory selectively received under the filtering condition “0001”,i.e.; “http://www/dirA/0001/index.html”, “http://www/dirA/0001/u1.png”,and “http://www/dirA/0001/u2.png”, are stored in the cache memory asshown in FIG. 48A.

Further, the CPU 147 varies the filtering conditions in the transportdecoder 141 so as to selectively receive packets having atable_id_extension value of “0003” upon reading a row 711 shown in FIG.44. In this way, all the files belonging to a directory selectivelyreceived under the filtering condition “0003”, are additionally storedin the cache memory in a sequential manner as shown in FIG. 48C. The CPU147 controls display of images depicted in FIG. 50A according to htmldata shown in FIG. 49. In this case, the file “jump.html” may also beconsidered as a reference file from the standpoint of a referred file“u1.png” because the file “jump.html” refers other referred files“u1.png” and so on.

In order to receive a referred file “http://www/dirA/0002/jump.html”,the CPU 147 varies the filtering conditions in the transport decoder 141so as to selectively receive packets having a table_id_extension valueof “0002” according to the description on a row 713 in FIG. 44 when theoperator clicks a region displaying an image 721 depicted in FIG. 50. Inthis way, all the files belonging to a directory selectively receivedunder the filtering condition “0002”, are additionally stored in thecache memory in a sequential manner as shown in FIG. 48C.

In order to store upcoming data, the data stored in the cache memory areerased partially in the order in which data are stored. In this case,the file “http://www/dirA/0001/index.html” has already been erased asdepicted in FIG. 48C.

The CPU 147 controls to display an image shown in FIG. 50B by referringthe files “http://www/dirA/0001/u1.png”, “http://www/dirA/0001/u2.png”,and http://www/dirA/0002/u4.png” those have already been stored in thecache memory when the referred file “jump.html” specified by the row 713depicted in FIG. 44 is html data shown in FIG. 49.

Thus, display of images according to files belong to several differentdirectories (groups) can be carried out even when these files arecontained in one reference file. In this way, referred files andrelevant data commonly used in a plurality of reference files can bestored as a package of data.

In this case, the referred files and the relevant data may also betransmitted and be received as one unitized file similar to that ofshown in FIG. 37 and FIG. 38.

The transmitter in this embodiment may automatically change directorynames into file names having a certain number of digits and certain kindof characters capable of reading by the transport decoder similar to thesecond embodiment. In that case, just the directory names may bechanged, while the file names remains the same. For example, a part“/music/” preceding to “jump.html” may be changed into characters “0002”having a certain number of digits and certain kind of characters capableof reading by the transport decoder as a result of recognition of thepart “/music/” as a directory name when the directory name of the file“http://www/dirA/music/jump.html” is changed.

One unitized file in which a plurality files linked with one another, asshown in FIG. 37 and FIG. 38 may be transmitted and received by usingone common module_id in the first embodiment through the thirdembodiment of the present invention.

The automatic reference tag(s) in which the image(s) is pasted theretois used in this embodiment. Other kinds of automatic reference tags, forexample style tags which define styles of the reference file may equallybe used. In this embodiment, a plurality of files are transmitted withthe same module_id, and the files having the same module_id are storedin the cache memory. The filtering conditions are varied when noexistence of the files having the same module_id is detected during thedata reference in the cache memory. The filtering conditions, however,could remain the same as the filtering conditions currently defined.This could occur when a file out of plural files contained in adirectory, has not been received yet. In that case, it is not necessaryto vary the filtering conditions of the transport decoder further.

As described in the previous embodiments, the desired HTML file(s) canbe extracted solely with the transport decoder without storing thecorrespondence table by assigning selecting conditions for specifying atleast one or plural files to the header field of the packets, theselecting conditions including a certain number of digits and certainkinds of characters capable of directly reading by the transportdecoder.

1-6. Other Embodiments

Selection of the referred file with the transport decoder can further beaccelerated in the first embodiment through the third embodiment bypreviously detecting the existence thereof within the reference file andthen varying the filtering conditions in the transport decoder as theexistence detected, rather than upon completion of data recognition foreach row.

Although, files are transmitted through both the DSM-CC object carouseland the DSM-CC data carousel on the MPEG 2 transport stream, anyprotocols capable of performing similar data processing may be used.

Though, the file name being converted is indicated with both a PID and amodule_id as a series of characters in the embodiments describedearlier, the PID may be retrieved from the PAT and the PMT, or may alsobe retrieved from a combination of other identifiers selected at anoption which allows the similar data processing.

The transmitter repeatedly transmits all the files, and the receiverobtains a desired file(s) by varying the filtering conditions infiltering means and displays it. In this way, it is possible to providea data communication system and a method thereof in which it appears tothe operator that the information is obtained in the receiver ininteractive ways according to the operations by him/herself withoutoutputting a command for transmission to the transmitter.

Although, the transmission of digital data performed in the satellitebroadcasting has been described in the embodiments described earlier,the transmission of digital data in the present invention may also beapplied to digital terrestrial broadcasting, and wire broadcasting suchas cable television in similar manners.

While module identifiers of HTML files, making up the front page beingdisplayed initially in the services, are assigned in the control dataPMT in the embodiments described earlier, the module identifiers may bestored in a storing part of the transmitter as fixed values. Forexample, they may be set instead of the table_id_extension of a filebeing transmitted initially when the operator switches the servicecurrently received to some other service.

The HTML files comprising the front page may be transmitted to thereceiver in a shorter period of time than other files during therepeated transmission. This is because less time lag for entering theservice is preferred, and entering in the service is not allowed withoutthe HTML files comprising the front page.

In the embodiments described earlier, the transport decoder selects adesired file(s) by referring to both the PIDs and thetable_id_extensions assigned to the files being transmitted by thetransmitter because all the files belong to the directory “¥weather”,and for example, the file name is indicated as /0001/0001.html in thecorrespondence table. The transport decoder may select the desiredfile(s) by using one of the PIDs and the table_id_extensions. Thetransport decoder may select the desired file(s) by using either one ofthe PIDs or the table_id_extensions. Further, the transport decoder mayuse the table_id in addition to both the PIDs and thetable_id_extensions. In other words, any identifiers which may directlybe recognized by the transport decoder can be used even when they arestored in other regions in the headers.

In the first embodiment, HTML data was transmitted as a single service,i.e., without video data and audio data. However, in another embodiment,HTML data can be transmitted with video data and audio data, together asone service, and the service may be displayed on the monitor after ofsynthesizing the data.

Further, data transmission of the HTML data has been described inaforementioned embodiments, other self-descriptive data such as standardgeneralized markup language (SGML) data or extensible markup language(XML) data may also be adopted to the present invention in similarmanner. In addition, image data which is referred by the HTML data, maybe generated in other formats, such as JPEG (.jpg) format than thegraphics interchange format (.gif) used in the earlier embodiments.Although, a tag <HREF> is employed as a reference command(s) forreferring other file(s) in the earlier embodiments, other commands mayalso be used in similar manner.

In order to select a specific region displayed on the monitor, theoperator moves the cursor freely on the monitor in the earlierembodiments. The control of the cursor depend on the operating system(not shown) installed in the receiver. The control may also be performedunder the display program.

The movement of the cursor may be restricted so as to move within aselectable region alone. The CPU detects that a region is selected inthe case of inputting the command “SET” by the operator during a periodin which the region is specified as a selectable region when images aredisplayed on the monitor according to a specific HTML file. For example,a region located at the upper left of the monitor is considered as theselected region when the command “SET” is inputted by the operator. Onthe contrary, a region located right under the region currently selectedmay be considered as the selected region when the operator enters acommand to move the cursor downwardly in the case of varying filteringconditions. Similar manners can also be adopted to all other directionsfor detecting the selected region. The selected region can be specifiedby detecting the direction in the command inputted with the remotecontroller by using all the coordinates being stored.

In the earlier embodiments, module identifiers of HTML files, comprisingthe front page being displayed initially in the services, are assignedto the additional information fields in the control data PMT. However,the module identifiers of the HTML files themselves may be assigned tothe additional information fields in the control data PMT. For example,“¥weather¥forecast.html” is stored in the additional information fieldswhen a file “¥weather¥forecast.html” is the front page displayedinitially in the service. In that case, the filtering conditions in thetransport decoder can be set by using a module identifier obtained fromthe correspondence table shown in FIG. 15.

While, unencoded data are transmitted by the transmitter in the earlierembodiments, the data being transmitted may be scrambled by thetransmitter and decoded with the receiver.

Both a computer software and the CPU are used for realizing functions ofthe block diagram shown in FIG. 1 in the above embodiments, there is nolimitation of realizing any of the functions by a computer hardware. Inaddition, a part of the functions or all of these may be realized by acomputer hardware such as logic circuits or the like.

In the embodiment described earlier, the display program is stored inthe ROM. Alternatively, the display program can also be installed oncein computer readable data storing mediums such as IC cards or CD-ROMs,and then storing the program in a nonvolatile memory through an IC carddrive or a CD-ROM drive. Further, the display program may be downloadedinto the nonvolatile memory through a communication line.

The program may also be incorporated with carrier waves and theresulting data may be transmitted as computer data signals.

1) The digital data communication system according to the presentinvention is characterized in that, the system comprises a transmitterand a receiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) display data generating means for generating display data accordingto the outputted data, and

b3) selecting condition varying means for varying the selectingcondition,

C) wherein c1) the file storing means stores files formed ofself-descriptive data which includes a reference command for referringanother file, and wherein the identifier of each file includescharacters directly being selected by the selecting condition varyingmeans,

c2) the display data generating means generates display data accordingto the self-descriptive data outputted by the selective receiving means,and

c3) the selecting condition varying means provides an identifierassigned to a file so as to obtain the file specified by the referencecommand in the self-descriptive data to the selective receiving means.

Thus, the files formed of self-descriptive data which includes thereference command for referring another file are repeatedly transmittedby the transmitter, and the receiver selectively receives desired filesin accordance with the selecting condition set therein and the receivergenerates display data according to the self-descriptive data. In thisway, the display data can be displayed on a display means. Also, theselecting condition is varied so as to obtain the file specified by thereference command in the self-descriptive data, so that the filesrequired for display can be received. In this way, the files solelyrequired for display can be displayed on the display means withoutstoring files not required for the display. Consequently, the filesformed of self-descriptive can be displayed even when data storingcapacity of the receiver is small.

Further, the identifier of each file includes characters directly beingselected by the selecting condition varying means of the receiver, andthe transmission means transmits the files packetized with identifiersuniquely assigned thereto, and the selective receiving means selectivelyreceives the packetized files having predetermined identifiers inaccordance with a selecting condition set therein, and the selectingcondition varying means provides the identifier assigned to the file soas to obtain the file specified by the reference command in theself-descriptive data to the selective receiving means. Consequently,desired files can be selected without using data representingcorrespondence thereamong.

3) The digital data communication system according to the presentinvention is characterized in that, the system further comprises displaymeans for displaying the display data generated by the display datagenerating means, and the selecting condition varying means varies theselecting condition set in the selecting means so as to select a filespecified by the reference command when one of a plurality of regionsdisplayed on the display means which is specified by the referencecommand is selected thereon. Consequently, the files formed ofself-descriptive data can be displayed on the display means withoutstoring files not required for the display, while switching the displayat an option of the operator.

The digital data communication system according to the present inventionis characterized in that, the files stored in the file storing means aredivided into groups according to the identifiers assigned thereto, andthe selecting means divides the self-descriptive data being outputtedinto groups by using the identifiers and outputs the dividedself-descriptive data therefrom. In this way, for example, chargeabledata can easily be distinguished from data free of charge by justassigning different directory names.

4) The digital data communication system according to the presentinvention is characterized in that, the data converting means convertsboth the identifier of each file and an identifier of the referencecommand into characters directly be selected by the selecting means. Inthis way, it is not necessary to specify the identifiers in charactersdirectly being selected by the selecting means when self-descriptivedata of the file to be transmitted is generated, so that theself-descriptive data can be generated in any other type of identifiers.

5) The digital data transmitter according to the present invention, eachof the files stored in the file storing means consist ofself-descriptive data including a reference command for referringanother file, and an identifier of the each file, consisting ofcharacters directly being selected by selective receiving means in areceiver, and the transmission means transmits the packetized files withunique identifiers. In this way, it is not necessary to prepare datarepresenting correspondence between identifiers assigned to files to beselected by the receiver and the selecting condition set in theselecting means. Consequently, desired files can be selected at a highspeed.

6) The digital data transmitter according to the present invention, boththe identifier of the each file and an identifier of the referencecommand are converted into characters directly be selected by selectingmeans in the receiver according to a rule for conversion whenidentifiers of the files stored in the file storing means are providedin a form incapable of directly selecting by the selecting means. Inthis way, it is not necessary to specify the identifiers in charactersdirectly being selected by the selecting means when self-descriptivedata of the file to be transmitted is generated, so that theself-descriptive data can be generated in any other type of identifiers.

7) The digital data transmitter according to the present invention ischaracterized in that, the data outputted from the selective receivingmeans forms a file consisting of self-descriptive data including areference command for referring another file, and the display datagenerating means generates display data according to theself-descriptive data outputted by the selective receiving means, andthe selecting condition varying means provides an identifier of a fileas the selecting condition to the selective receiving means so as toobtain the file specified by the reference command in theself-descriptive data. In this way, the files solely required for thedisplay can be displayed on the display means without storing files notrequired for the display. Consequently, the files formed ofself-descriptive data which refer one another can be displayed even whendata storing capacity of the receiver is small.

10) The digital data communication system according to the presentinvention is characterized in that, the files stored in the file storingmeans are divided into groups according to the identifiers assignedthereto, and the selecting means divides the self-descriptive data beingoutputted into groups by using the identifiers and outputs the dividedself-descriptive data therefrom. In this way, the files thus receivedcan be divided into groups. Consequently, for example, chargeable datacan easily be distinguished from data free of charge by dividing intoseparate groups.

The grouping described above can also be carried out by substituting theidentifiers assigned to the files stored in the file storing means withboth directory names and file names belonging thereto, and thepacketized files selected by the selecting means are divided into groupsunder the directory basis thereby. 11) The digital data communicationsystem according to the present invention is characterized in that, thefiles divided in the same group are transmitted with the same packet id.In this way, the received files can be divided into groups by using thePID.

12) The digital data receiver according to the present invention ischaracterized in that, the selecting means divides the packetized filesselected by the selecting means into groups under the directory basisthereby. In this way, the files thus received can be divided intogroups. Consequently, for example, chargeable data can easily bedistinguished from data free of charge by just assigning differentdirectory names.

18) The method of communicating digital data according to the presentinvention is characterized in that, a plurality of files are repeatedlytransmitted after packetizing the files according to a transmissionprotocol with identifiers uniquely assigned thereto in a transmittingstation, each of the files consisting of self-descriptive data includinga reference command for referring another file, the identifier of theeach file consisting of characters directly being selected by areceiving station, and the following steps are performed in a receivingstation, the packetized files having predetermined identifiers areselectively received in accordance with a selecting condition settherein, and display data are generated in accordance with theself-descriptive data contained in the packetized files and the displaydata are outputted, and the identifier of the file is varied as theselecting condition so as to obtain the file specified by the referencecommand in the self-descriptive data.

In this way, the files formed of self-descriptive data can be displayedon the display means without storing files not required for the displayin the file storing device, while not preparing data representingcorrespondence of files to be selected.

19) The data communication system according to the present invention ischaracterized in that, the system comprises a transmitter and areceiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) received data storing means for storing data contained in thepacketized files each having same identifier in one independent filebasis,

b3) display data generating means for generating display data accordingto the outputted data, and

b4) selecting condition varying means for varying the selectingcondition; and

C) wherein c1) the file storing means stores files formed ofself-descriptive data which includes a reference command for referringanother file,

c2) the transmission means assigns one module identifier includingcharacters capable of being read directly with the selective receivingmeans to both a reference file which refers other files and a referredfile which is referred by the reference file, and transmits thereference file and the referred file, and

c3) the display data generating means generates display data accordingto self-descriptive data contained in the reference file, and generatesanother display data according to a desired referred file which is readout thereby from the received data storing means.

In this way, the referred file can further be selectively received byjust setting the selecting condition for selecting the reference filewithout preparing data representing correspondence between the referencefile and the file to be selected. Consequently, display data accordingto the reference file which includes the referred file, can be displayedquickly. As a result, desired files can be selected at a high speedwithout storing all the files.

20) The data receiver according to the present invention ischaracterized in that, the receiver comprises selective receiving meansfor selectively receiving packetized files having predeterminedidentifiers in accordance with a selecting condition set therein andoutputting data contained in the packetized files, received data storingmeans for storing the outputted data each having same identifier under afile basis, display data generating means for generating display dataaccording to the outputted data, and selecting condition varying meansfor varying the selecting condition, wherein the packetized files thusreceived are one of a reference file formed of self-descriptive datawhich includes a reference command for referring another file and areferred file which is referred by the reference file, and oneidentifier including characters capable of being read directly with theselective receiving means is assigned to these files, and whereindisplay data generating means generates display data according toself-descriptive data contained in the reference file, and generatesanother display data according to a desired referred file which is readout thereby from the received data storing means, and wherein theselecting condition varying means varies the selecting condition so asto selectively receive packetized files each assigned same identifierwith that of a specific reference file in order to selectively receivethe specific reference file.

In this way, the referred file can further be selectively received byjust setting the selecting condition for selecting the reference filewithout preparing data representing correspondence between the referencefile and the file to be selected. Consequently, display data accordingto the reference file which includes the referred file, can be displayedquickly. As a result, desired files can be selected at a high speedwithout storing all the files.

21) The data receiver according to the present invention ischaracterized in that, file to be automatically referred can selectivelybe received without setting the selecting condition for selectivelyreceiving the desired file to be automatically referred as a result ofreading a reference file when the reference file is a file including anautomatic reference tag. In this way, display data of a file includingthe file to be automatically referred can be generated more quickly.

22) The data receiver according to the present invention ischaracterized in that, the referred file is selectively received as itis when selective receipt of the reference file is initiated because thereference file and the referred file are linked with each other.

23) The data receiver according to the present invention ischaracterized in that, the reference file and the referred file comprisea unitized file. In this way, desired files can selectively be receivedwhen selective receipt of the one unitized file is initiated.

24) The method of communicating digital data according to the presentinvention is characterized in that, a plurality of files stored in atransmitting station after packetizing the files according to atransmission protocol are repeatedly transmitted with identifiersuniquely assigned thereto in the transmitting station, and the followingsteps are performed in a receiving station, the packetized files havingpredetermined module identifiers are selectively received in accordancewith a selecting condition set therein, data contained in the packetizedfiles each having same identifier are stored in one independent filebasis, and display data are generated according to the outputted data,wherein one module identifier including characters capable of being readdirectly with the receiving station is assigned to both a reference filewhich refers other files and a referred file which is referred by thereference file in the transmitting station, and wherein the followingsteps are performed by the receiving station, the selecting condition isvaried so as to selectively receive packetized files each assigned sidentifier with that of a specific reference file in order toselectively receive the specific reference file, and display data isgenerated according to self-descriptive data contained in the referencefile, and generates another display data according to a desired referredfile which is read out thereby.

In this way, the referred file can further be selectively received byjust setting the selecting condition for selecting the reference filewithout preparing data representing correspondence between the referencefile and the file to be selected. Consequently, display data accordingto the reference file which includes the referred file, can be displayedquickly. As a result, desired files can be selected at a high speedwithout storing all the files.

26) The data communication system according to the present invention ischaracterized in that, the system comprises a transmitter and areceiver,

A) the transmitter including:

a1) file storing means for storing a plurality of files, and

a2) transmission means for repeatedly transmitting the files packetizedthereby in accordance with a transmission protocol, the packetized filesuniquely assigned identifiers;

B) the receiver including:

b1) selective receiving means for selectively receiving the packetizedfiles having predetermined identifiers in accordance with a selectingcondition set therein and outputting data contained in the packetizedfiles,

b2) received data storing means for storing data contained in thepacketized files each having same identifier in one independent filebasis,

b3) display data generating means for generating display data accordingto the outputted data, and

b4) selecting condition varying means for varying the selectingcondition; and

C) wherein c1) the file storing means stores a plurality of referencefiles formed of self-descriptive data which includes a reference commandfor referring a plurality of other files,

c2) the transmission means assigns one module identifier includingcharacters capable of being read directly with the selective receivingmeans to the reference files and transmits the reference files,

c3) the display data generating means generates display data accordingto self-descriptive data contained in the reference files, and generatesanother display data according to desired referred files which are readout thereby from the received data storing means, and

c4) the selecting condition varying means uses the module identifier asthe selecting condition.

In this way, a plurality of referred files to be selected are receivedas one unitized file. Consequently, display data according to thereference file which includes the referred file, can be displayedquickly. As a result, desired files can be selected at a high speedwithout storing all the files.

27) The digital data receiver according to the present invention ischaracterized in that, the receiver comprises selective receiving meansfor selectively receiving packetized files having predeterminedidentifiers in accordance with a selecting condition set therein andoutputs data contained in the packetized files, received data storingmeans for storing data contained in the packetized files each havingsame identifier in one independent file basis, display data generatingmeans for generating display data according to the outputted data, andselecting condition varying means for varying the selecting condition,wherein the packetized files thus received are one of a reference fileformed of self-descriptive data which includes a reference command forreferring a plurality of other files and a referred file which isreferred by the reference file, and wherein one identifier includingcharacters capable of being read directly with the selective receivingmeans is assigned to the referred files through the reference file, andwherein the display data generating means generates display dataaccording to self-descriptive data contained in the reference file, andwherein the selecting condition varying means varies the selectingcondition so as to selectively receive packetized files each assignedsame identifier with that of a specific reference file in order toselectively receive the specific reference file in accordance with dataof the reference file.

In this way, a plurality of referred files to be selected are receivedas one unitized file. Consequently, display data according to thereference file which includes the referred file, can be displayedquickly. As a result, desired files can be selected at a high speedwithout storing all the files.

28) The data receiver according to the present invention ischaracterized in that, same module identifier with that of the referredfiles is assigned to the reference file. In this way, the referred filecan further be selectively received by just setting the selectingcondition for selecting the reference file without preparing datarepresenting correspondence between the reference file and the file tobe selected. Consequently, display data according to the reference filewhich includes the referred file, can be displayed quickly. As a result,desired files can be selected at a high speed without storing all thefiles.

29) The data receiver according to the present invention ischaracterized in that, the receiver comprises selective receiving meansfor selectively receiving packetized files having predeterminedidentifiers in accordance with a selecting condition set therein andoutputs data contained in the packetized files, received data storingmeans for storing data contained in the packetized files each havingsame identifier in one independent file basis, display data generatingmeans for generating display data according to the outputted data, andselecting condition varying means for varying the selecting condition,wherein the packetized files thus received are one of a reference fileformed of self-descriptive data which includes a reference command forreferring another file and a referred file which is referred by thereference file, and one identifier including characters capable of beingread directly with the selective receiving means is assigned to thesefiles, and wherein display data generating means generates display dataaccording to self-descriptive data contained in the reference file, andgenerates another display data according to a desired referred filewhich is read out thereby from the received data storing means, andwherein the selecting condition varying means extracts charactersdirectly be selected by the selective receiving means out of absolutepath assigned to the referred files and provides the characters to theselective receiving means as the selecting condition so as toselectively receive packetized files each assigned same identifier withthat of the reference file in order to selectively receive the referencefile.

In this way, the file formed of self-descriptive data can be displayedon the display means without storing files not required for the displaybecause a part of the absolute path assigned to the referred files isused as the selecting condition. Consequently, a file referred byanother can be displayed even when data storing capacity of the receiveris small.

Definition of words used in the appended claims, and correspondencebetween these words to the words used in the embodiments described aboveare as follows.

The word “receiver” is a device, at least capable of selectivelyreceiving a desired service contained in a desired transport stream outof a plurality of transport streams being transmitted. The deviceincludes a video cassette recorder which incorporates an apparatus socalled a set-top box, or a television set and the like having thefunctions of a set-top box.

The word “self-descriptive data” is data assigned its displayinformation such as display positions of character data, its charactersize, information as to graphic data to be referred. For example, SGMLdata, HTML data, XML data, data defined under coding of multimedia andhypermedia information part 5 in ISO/IEC 15522-5 (MHEG standard) and thelike are included in the self-descriptive data.

The word “program storage medium” includes a data storing medium storingprogram(s) performed by a CPU such as ROMs, RAMs, hard disks, flexibledisks, CD-ROMs and the like. Further, the programs correspond to thememory 27 and the hard disk 26 depicted in FIG. 2 in the embodimentsdescribed above.

While the invention has been described in its preferred embodiments, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes within the purviewof the appended claims may be made without departing from the true scopeand spirit of the invention in its broader aspects.

What is claimed is:
 1. A digital data receiver comprising: selectivereceiving means for selectively receiving packetized files havingpredetermined identifiers in accordance with a selecting condition settherein and for outputting data contained in the packetized files,received data storing means for storing data contained in the packetizedfiles, each of the packetized files having a same identifier in oneindependent file basis, display data generating means for generatingdisplay data according to the outputted data, and selecting conditionvarying means for varying the selecting condition; wherein thepacketized files thus received are files related to one another, areconnected in series as one unitized file and are assigned one identifierincluding characters capable of being read directly with the selectivereceiving means, and wherein the selecting condition varying meansextracts characters to be selected by the selective receiving means outof an absolute path assigned to the packetized files and provides thecharacters to the selective receiving means as the selecting conditionso as to selectively receive packetized files that are each assigned thesame identifier.
 2. The receiver in accordance with claim 1: wherein thefiles related one another include at least a reference file formed ofself-descriptive data which includes a reference command for referringanother file and a referred file which is referred by the referencefile; and wherein the packetized files assigned the absolute path arethe referred files.
 3. The receiver in accordance with claim 2: whereineach referred file is distinguished by identifying a delimiter ofreferred files connected in series.